Well, that's
curious!
Dictionary is badly broken... Strange app to have gone down in flames like that.
This sure is confusing. What exactly is curious? What makes you think Dictionary is broken? And have you selected the '
All' tab in Dictionary's window to see what's available?
What I initially found curious - sorry for being a bit obscure - is that as per joemike
(Type "OS X" in the Apple Dictionary.)
Only Wikipedia has an entry for OSX or OS X either of which jump to MacOS.
Apple Dictionary in High Sierra dropped all OS X details without even cross-referencing it to macOS.
But even more curious is that when I booted into 10.13.3 just now I found that typing "OS X" in the Apple Dictionary (search box) generates the same results seen in my 10.12.6 "curious" screenshot.
Even if the originally noted anomalies didn't leave you thinking "broken", I think that as respects them in combination with what's been introduced here and in my immediately previous post, "broken" is an appropriate word.